The present invention relates to a restraining system for hollow fibres used in membrane filtration systems.
A number of different types of restraining systems usually in the form of a welded plastic mesh cage have been used in the past, however, these suffer from lack of rigidity when large apertures are required in the mesh to allow for fluid flows and are difficult to repair should any portion of the mesh be broken during transport, installation or use. While such known restraining systems are cheap and simple to manufacture they suffer from a lack of robustness in many required installations.
The present invention seeks to overcome or at least ameliorate one or more of the disadvantages of the prior art or at least provide the public with a useful alternative.
According to one aspect, the present invention provides a restraining system for hollow fibres including a plurality of longitudinally extending elements spaced from one another and supported by a number of discrete spacer elements, each spacer element extending generally transverse of said longitudinal elements such that in combination with said longitudinal elements they define a cage-like structure.
For preference, the cage-like structure is tubular. Preferably, the longitudinal elements are rods and the spacer elements are in the form of rings. It will be appreciated that the rings may of any geometric shape and are not limited to a circular shape. Similarly, the tubular structure and rods may be of any geometric cross sectional shape.
In one preferred form, each ring has a number of radially extending engagement formations for releasably engaging an associated rod. The formations may be in the form of part-circular opposed flanges spaced to provide a socket having an interference or snap-fit with the associated rod.
In another preferred form, each ring has a number of radially extending cut-outs spaced around its periphery, each cut-out being sized and shaped to form an interference or snap-fit with an associated rod. Preferably, the internal surface of each ring is bevelled along each internal edge. For further preference, the internal surface of each ring is providing with a cushioning element. Preferably, the cushioning element is formed of a foam material and extends past the length of each ring at both ends so as to overlap the internal edges of each ring.
The spacer elements may be formed from a number of sub-elements which are fixed together in use.
The cut-outs or sockets are preferably equally-spaced around the periphery of the ring.
For preference, the rods have a reduced diameter or width at the location where they engage with an associated spacer. Preferably, the reduced diameter is provided by a circumferential groove or slot.
The components of the system are preferably formed of generally rigid plastics material, typically nylon and acrylonitrile butadiene styrene (ABS). The components can be moulded or machined to the desired configuration. The cut-outs are preferably part circular in cross section with an opening slightly smaller than the diameter to provide for snap-fitting retention of the rods.